1. Field of the Invention
The present invention relates to a method and apparatus for feeding a sheet that is to be applied to a wiring harness, and particularly to be wound around a wiring harness. The invention also relates to a sheet cutting apparatus and an adhesive double-coated tape adhering apparatus.
2. Description of the Related Art
A wiring harness xe2x80x9cWxe2x80x9d for an electrical wiring system of an automotive vehicle or a copier is shown in FIG. 5. The wiring harness W includes a plurality of wires xe2x80x9caxe2x80x9d that are bound and branched. The wiring harness W also includes connectors c that are connected at ends of the respective wires xe2x80x9caxe2x80x9d. Sheet pieces Sxe2x80x2 of specified sizes are wound manually around the outer surfaces of bundles of the wires xe2x80x9caxe2x80x9d in necessary positions to protect the wires xe2x80x9caxe2x80x9d. The sheet pieces Sxe2x80x2 are made, for example, of a polyvinyl chloride (PVC) or any other suitable material that may be selected in view of electrical insulation or watertight properties. An adhesive layer is formed adjacent a side edge of each sheet piece Sxe2x80x2, as shown in FIG. 6, to prevent the sheet pieces Sxe2x80x2 from being peeled off the wiring harness and to facilitate winding the sheet piece Sxe2x80x2 onto the wiring harness. The adhesive layer is formed by employing a double-coated adhesive tape t that has a separable strip e covering one adhesive surface of the tape t. In particular, one adhesive surface of the tape t is adhered adjacent an edge of the sheet piece Sxe2x80x2, and the separable strip e covers the adhesive surface of the tape t that is not adhered to the sheet piece Sxe2x80x2. The separable strip e is peeled off, as indicated by the arrow in FIG. 6, when the sheet piece Sxe2x80x2 is about to be applied to the wiring harness W.
Conveying harness-assembling boards along a conveyor generally produces wiring harnesses W of this type. Operators at various stations along the conveyance line then successively mount various parts on the respective harness assembling boards. Parts mounted along this conveyance line include the sheet pieces Sxe2x80x2, which conventionally have been stored in containers on the harness assembling boards or in containers at mount positions of the respective parts, as disclosed, for example, in Japanese Unexamined Patent Publication No. 7-235228.
A technique for adhering an adhesive double-coated tape t to a sheet S is disclosed in Japanese Unexamined Patent Publication No. 9-151007. This technique employs a rolled sheet S that is dispensed, and that is rolled again after the adhesive double-coated tape t is adhered thereto.
The technique for storing the sheet pieces Sxe2x80x2 in the containers requires an inefficient procedure of preparing the specified sheet pieces Sxe2x80x2 off the production line. Further, this prior art technique requires the number of containers to at least equal the number of harness assembling boards. Additionally, the containing operation is cumbersome because the parts for the different harness assembling boards must be stored in containers at the specified positions, and the containers must be capable of distinguishing the sheet pieces Sxe2x80x2 in the respective containers.
Further, a smaller amount of the sheet S is wound on one reel in the roll of the sheet S to which the adhesive double coated tape t is adhered because the sheet S becomes thicker at one side by an amount equal to the thickness of the tape t, and the sheet S is difficult to wind and dispense from the roll due to a difference in the thickness at the opposite sides.
Accordingly, it is an object of the present invention to improve operational efficiency in a production line.
The subject invention eliminates the preparation of sheet pieces by feeding a necessary number of sheet pieces to a specified position of a desired harness assembling board on a production line when the sheet pieces are necessary. Moreover, the invention eliminates the operation of peeling off a separable strip, thereby improving an operation efficiency by adhering an adhesive double coated tape to a sheet being dispensed from a sheet roll and separating the separable strip of the adhesive double coated tape before the sheet is cut to a specified length.
The invention is directed to a method for feeding sheets to be applied to a wiring harness. The method comprises a step of recognizing required sizes of sheets that are necessary to assemble the wiring harness. A recognition signal then may be generated. The method then comprises cutting one or more sheets dispensed from corresponding sheet rolls to specified lengths or sizes to form sheet pieces in accordance with the recognition signal. The method further comprises dropping the sheet pieces in positions corresponding to the respective harness assembling board. The dropping of the sheet pieces may be coordinated with the conveyance of the harness assembling boards along a conveyance system.
Preferably, the sheet pieces are dropped directly onto the respective harness assembling board. Accordingly, it is possible to recognize the sheet pieces that are necessary to assemble a wiring harness on each harness assembling board, to cut one or more sheets dispensed from corresponding sheet rolls to specified lengths and to supply the cut sheet pieces to each harness assembling board by dropping the cut sheet pieces at a specified position on each harness assembling board.
With such an arrangement, a desired number of sheet pieces of desired lengths can be supplied to the respective harness assembling boards in a production line. Thus, unlike the prior art, it is not necessary to prepare the sheet pieces beforehand, thereby improving operability and reducing the stock of the sheet pieces. The required length of the sheet pieces may be changed if the kinds of wiring harnesses to be assembled are changed. Such a change can be accommodated easily by adjusting a dispensed amount of the sheet.
According to this method, a plurality of sheet rolls of different widths may be prepared, and the sheets of the desired widths are dispensed from the respective rolls and cut to specified lengths in accordance with the recognition signal. Thus, sheet pieces having a plurality of different widths can be supplied, thereby increasing modes of wiring harnesses to be assembled. The number of the sheet rollers may correspond to the number of the different sheet widths necessary for one production line.
Each sheet may have an adhesive double coated tape provided with a separable strip adhered adjacent one side edge. The separable strip may be peeled off before the sheet is cut to the specified length. The presence of the separable strip does not hinder the travel of the sheet and, if the separable strip is peeled and the sheet pieces are dropped onto the harness assembling board, an operator need not peel the strip off.
Most preferably, the adhesive double coated tape is adhered to each sheet by adhering an end of the double coated tape that is dispensed from a tape roll to the sheet that is dispensed from the sheet roll. The remainder of the double coated tape is adhered to the sheet as the tape is dispensed from the tape roll by a dispensing force created as the sheet is dispensed.
At this stage, the separable strip is pulled apart from the sheet and peeled as the sheet is fed in accordance with the recognition signal. Thus, the sheet can be cut smoothly without the separable strip getting caught in a sheet cutting apparatus.
A specific construction of the sheet cutting apparatus comprises a feed roller that may be driven by an external force for feeding at least one sheet dispensed from at least one sheet roll. The apparatus also comprises a pressure roller that is movable toward and away from the feed roller with the sheet located between the feed roller and the pressure roller. The apparatus further comprises a cutter for cutting the sheet into sheet pieces. The pressure roller is pressed against the feed roller that is rotated to feed the sheet by a specified length, and the fed sheet is cut by the cutter in accordance with the recognition signal.
The feed roller of the above-described sheet cutting apparatus is rotated by an amount corresponding to the length of the sheet to be fed. At this time, the pressure roller is pressed against the feed roller with the sheet located between the pressure roller and the feed roller. Thus, the sheet of a specified length is fed and cut. The sheet cannot be fed unless the pressure roller is pressed against the feed roller. Therefore, the sheet of a specified length can be fed by constantly rotating the feed roller and pressing the pressure roller against the feed roller for a time corresponding to an amount by which the sheet is to be fed. The feed roller may not be rotated constantly, but may be rotated while the pressure roller is pressed against feed roller. In other words, the feed roller may be rotated during a period including a contact period with the pressure roller in accordance with the recognition signal. The sheet of a specified length can also be fed by constantly pressing the pressure roller against the feed roller and rotating the feed roller by an amount by which the sheet is to be fed. In such a case, the pressure roller is left spaced apart when the sheet is located between the two rollers.
A specific construction of a tape adhering apparatus comprises one or more sheet reels for supporting corresponding sheet rolls, and one or more tape reels for supporting corresponding rolls of adhesive double coated tapes. The sheets are dispensed from the sheet rolls by an external force, and the adhesive double coated tapes are dispensed from the tape reels while back tensions are applied to the tape. The dispensed ends of the tapes then are adhered to the corresponding sheets.
The tape adhering apparatus described above enables the adhesive double coated tape to be dispensed from the reel in a tense state as the sheet is dispensed. One adhesive surface of the tape then is adhered to the sheet.
A specific construction of an apparatus for feeding sheets comprises a detector at a specified position for detecting when a harness assembling board is at that position. The sheet cutting apparatus preferably is provided above the harness assembling board at the specified position. At least one sheet from the tape adhering apparatus is introduced to the sheet cutting apparatus. The separable strip of the adhesive double coated tape that been adhered to the sheet then is peeled from the sheet by turning the separable strip around a bar located before rollers of the sheet cutting apparatus. The peeled separable strip then is pulled by rollers that are rotated in synchronism with the feed roller of the sheet cutting apparatus.
The above-described sheet feeding apparatus has the advantages of the sheet cutting apparatus and the tape adhering apparatus, as described above. Further, since the separable strip is peeled in synchronism with the feed of the sheet, the sheet can be cut smoothly without the separable strip getting caught in the sheet cutting apparatus. Thus necessary sheet pieces can be fed smoothly onto the harness assembling boards.
These and other objects, features and advantages of the present invention will become apparent upon reading of the following detailed description of preferred embodiments and accompanying drawings.